Multiple Effect Evaporators
Engineering and Manufacturing Evaporators for Chemical Process Industries
Multiple Effect Evaporators
Swenson’s multiple-effect evaporators are cost effective when high-pressure steam is available to heat the system.
Benefits of Multiple-Effect Evaporators
- Optimize energy usage by leveraging vapours generated from one effect to drive another (steam economy)
- Reduce overall energy requirements
- Increase thermal efficiency
How Multiple Effect Evaporators Work
Multiple-effect configurations combine two or more evaporator bodies to conserve steam. Live steam which is condensed in the first-effect heat exchanger only. Water evaporated in the first-effect vapour body is condensed in the second-effect heat exchanger, which provides energy for evaporation in the second-effect vapour body—and so on for additional effects.
Vapour from the last effect flows to a condenser. The last-effect vapour body is maintained at a high vacuum with a steam ejector or mechanical vacuum pump.
For the same overall process conditions, the evaporator with more effects will require less steam. The evaporation in each effect will be approximately 0.7 to 0.9 times that of the steam condensed in the first-effect heat exchanger. In actual practice, the steam economy can vary widely because of differences in feed temperature and other energy requirements such as heats of dilution and crystallization.
The number of effects is limited by the total available temperature difference between the plant steam and the cooling water temperature. Process liquors with high boiling point elevations typically operate with fewer effects.
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